Background: Both warfarin and nonvitamin K antagonist oral anticoagulants (NOACs) are increasingly used for thromboembolic prevention in patients with nonvalvular atrial fibrillation (NVAF). However, there are limited data concerning anticoagulation for left atrial (LA) thrombus or sludge. We aimed to determine the efficacy of warfarin and NOACs in LA thrombus or sludge in patients with NVAF or atrial flutter (AFL). Materials and Methods: Seventy-two patients with LA thrombus or sludge were analyzed who were scheduled for catheter ablation of NVAF or AFL between December 2015 and November 2018. Baseline demographics, the nature and duration of anticoagulation therapy and LA thrombus or sludge resolution were recorded. Results: After receiving anticoagulation therapy for 101.5 (76.3-151) days, 44 patients (61.1%) demonstrated LA thrombus or sludge resolution, including 10 (58.8%) for warfarin, 15 (57.7%) for dabigatran and 19 (65.5%) for rivaroxaban (with no significant differences among these anticoagulants). After either prolonged anticoagulation, increased dosage or a change in anticoagulant, 14 patients underwent a third transesophageal echocardiography after 194.5 days (164.8-401.0) and an additional nine patients (12.5%) demonstrated LA thrombus or sludge resolution. Finally, 53 patients (73.6%) demonstrated complete resolution of LA thrombus or sludge, and this group had a lower CHA2DS2-VASc score (P = 0.044) and a lower rate of stroke history (P = 0.041). Conclusions: Compared with warfarin, dabigatran and rivaroxaban can also effectively resolve LA thrombus or sludge with no significant differences. Increasing the duration of anticoagulation, determining the optimal dosage of anticoagulants, and switching to another anticoagulant when necessary could be considered to improve treatment effectiveness. © 2019